1. Field of the Invention
The invention relates to marine work platforms in general, and to work platforms especially suited for use in a marsh environment in particular.
2. Prior Art
There are many coastal marshlands in the United States that cover rich petroleum reserves. These marshlands are home to a great diversity of wildlife. They serve as the nursery for a wide variety of commercially significant fish and shellfish, and they are the home to numerous mammals, reptiles, amphibians, and birds. Along the coast of the Gulf of Mexico, these marshes also provide wintering grounds to millions of migratory waterfowl. Some of the creatures that live in the marsh, such as the ringed sawback turtle, are endangered, and one of the principle difficulties they face is the loss of habitat.
Many of these marshes, and some of the most productive in terms of wildlife, are brackish. They exist in a delicate balance between freshwater draining from the land and saltwater entering from the sea. A change in this balance, particularly an increase in saltwater, can have disastrous results. An increase in salinity can kill the vegetation that thrive in the brackish waters. This vegetation is the bedrock on which the entire food chain of the marsh depends. As it dies, the marsh is no longer able to support life, and a vibrant ecosystem can disappear in an astonishingly short period of time.
The loss of the marsh grass can also threaten the physical existence of the marsh. Frequently, the only structure holding the underlying soil in place is the grass. As it dies, the tidal flow and ocean storms are able to carry away the fine silt that makes up the marsh. Thus, an influx of saltwater can literally erase an entire marshland ecosystem. Although described in terms of a brackish marsh, the foregoing explanation is equally applicable to freshwater marshes.
The exploitation of the petroleum reserves lying below the marshes is often a direct cause of such saltwater intrusion. To extract these reserves, a well must be drilled. This requires a work platform on which the drilling structure may be supported. On dry land, a platform may be erected on the ground, and the necessary equipment may simply be trucked to the site. In the open ocean, a work platform may be floated to the drill site and raised using a jack-up mechanism such as that illustrated in U.S. Pat. No. 5,833,396, which is hereby incorporated by reference in its entirety to the extent its teachings are not contrary to those contained herein.
Drilling in the marsh creates a unique set of difficulties. The land is frequently insufficiently solid to support trucks, which prevents the necessary equipment from being driven to the site. Also, the water in the marsh is too shallow to allow the equipment to be floated to the drill site, and the cost is too high and the equipment is too heavy for all the necessary equipment to be transported by helicopter or other aircraft. The solution most frequently employed is to dig canals in the marsh in order to create water deep enough to float in the drilling equipment. In addition to the other difficulties discussed below, this is a substantial expense in marsh drilling.
Probably the most significant drawback to the use of canals is that they provide a direct passage for saltwater to enter the marsh, with the environmentally disastrous results described above. For this reason, regulations have been passed in the United States restricting the creation of canals in the remaining coastal marshes. This creates a transportation problem for those wishing to drill in the marshes which may preclude the drilling of some wells altogether. Similar, difficulties can arise in other sensitive environments such as arctic tundra or any other location where canals may prove harmful. Therefore, a work platform meeting the following objectives is desired.